Development of human society is based on manufacturing industries, where mechanical properties of materials directly restrain a high-speed development of manufacturing industries, influence developments in fields of aerospace, national defense engineering, industry and agriculture, etc., and influence developments of modern science and technology. Mechanical properties of materials under actual load such as stretching, bending, and fatigue etc. are directly related to safety of industry and agriculture, safety of military equipments and safety of human lives and properties. With rapid development of micro-electromechanical systems (MEMS) and micro-imaging device in recent years, it has been found that changes in microstructure of a material may directly influence its macromechanical properties, thus it is very important to start a study in testing technologies of mechanical properties of materials based on changes microstructures.
Traditional testing technologies on conventional tension, bending, torsion and fatigue tests have been well developed, and can substantially meet the requirement on testing macromechanical properties such as strength and fatigue property. However, such tests are usually offsite tests, which cannot provide a real-time dynamic observation of microstructural profiles of a test piece during the tests. Thus, the inner mechanism of microstructural changes and macromechanical properties of a material cannot be effectively combined to characterize the performance of the material. Specifically, in the condition of an actual practice, the material and a product made of the material are usually under action of more than one load, such as a combination of tension and bending, a combination of bending and shear, a combination of tension and torsion, or the like, in which multiple loads exist at the same time. Mechanical property test in a single load manner cannot accurately reflect the loads applied on material and component in an actual situation, that is, no accurate evaluation can be made on mechanical properties of a material under action of complex load. For example, in consideration of experimental study, a material under action of a tension stress will break at a critical bending stress that is much smaller than its bending strength; and a material under action of a bending stress will break at a critical tension stress that is much smaller than its tensile strength. In current studies, a main way of applying a complex-load mode is accomplished by an irregular clamping device orientated at an angle to an axis of tension/compression of a test piece. Axial loading forces output from a driving source are applied along different axes or at different heights to provide an asymmetrical clamping, such that complex load, such as a combination of tension and bending, or a combination of compression and shear, occurs inside the material. Another way of applying complex load is accomplished by utilizing a complicated and expensive multifunctional material testing machine. However, such a testing machine can only apply certain type of complex load, two or more loads cannot be separately or successively applied, such that no accurate evaluation can be made on mechanical properties of a material and its product and inner mechanism of deformation and damage under the action of complex load, and thus popularization and application of material testing machine are significantly restrained.
With innovations in material science, manufacturing technology, various novel functional material are developed, performances of conventional materials have been improved and application ranges of such materials are extended, thus people have set higher demands on material properties and testing. Before the 1980's, a material testing machine is merely applied in a few fields, such as metal materials, etc. Today, application range of a material testing machine is not limited to metal materials, but has been widely used in all industries. Particularly, with wide use of novel ferroelectric/ferromagnetic, thermomagnetic and semiconductor materials, mechanical properties of material in a multi-physical field, such as a force-electric-thermal-magnetic field, would be more important. Existing commercial testing machine can seldom fulfill the requirements of simulation and testing of properties of a material in the above-described multi-physical field. Thus, it is a trend to develop novel testing machine that can test properties of a material in a multi-physical field.